ADU rules in Alpine

Alpine defines an ADU as a unit within and part of a principal dwelling, and detached accessory structures require a recorded agreement not to be used as a dwelling, dwelling unit, or accessory apartment. The only detached quasi-unit is a guest house, a separate conditional use limited to temporary occupancy on lots of 5 acres or more.

Internal ADUs (a subordinate dwelling unit within and part of a principal dwelling with its own cooking, sleeping, and sanitation facilities) are allowed, limited to one per owner-occupied single-unit detached dwelling, with a separate outside entrance on the side or rear. Listed as a permitted use in the TR-10,000, CR-20,000, CR-40,000, and CE-5 zones and as a conditional use in CE-50.

The ordinance sets no square-footage maximum; it requires the ADU to comply with all size and access specifications of the International Residential and Building Codes.

ADUs are permitted only in owner-occupied single-unit detached dwellings. An exception applies for a documented temporary absence of 3 years or less (job assignment, sabbatical, military or voluntary service) or placement in a hospital or care facility, if a temporary absence application is filed before the absence and the owner lived in the home at least 1 year prior. Owner occupant is defined at §3.01.110 (50 percent or more recorded ownership and primary residence).

A single-unit detached dwelling with an ADU must provide not less than 4 off-street parking spaces; garage and driveway spaces count, and at least one space must be designated for the ADU.

In the TR-10,000, CR-20,000, CR-40,000, and CE-5 zones ADUs are a permitted use requiring an ADU permit from the Building Department (in addition to any building permits). In the CE-50 zone ADUs are listed as a conditional use requiring approval by the designated review agency.

The ADU section itself sets no lease-term or tenant limits, but the special provisions of each residential zone (TR-10,000, CR-20,000, CR-40,000, CE-5) prohibit short term rentals, defined at §3.01.110 as lodging rented for 30 consecutive days or less. Utility meters must stay in the owner's name.